This question already has an answer here:
Floating stones are used to build this bridge
Ram Setu but now the NASA found it is under the sea however the floating stones how could sink in the ocean.
Updated: Its actually the story of war within Rama and Ravana by the way Rama and his army entering via floating bridge build by Nala. All the things are clear and understood.
Floating stones why
sunk in an ocean now.